An image processing technique was used to measure flow rate versus time in the study: A Continuous, Low Flow, Multiplexing Pumping System for Microfludidics Applications
First, raw data was collected by infusing blue dyed water through micro bore tubing and filming horizontal videos of the infusion. The videos were then cropped to only include the tubing. The cropping doesn't need to be perfect, since only vertical edge detection is performed, but including as few background pixels as possible will increase the acuracy of the algorithm.
The length of tubing in the frame was noted for later use in data processing.